“Pakistan on the Brink: The Future of America, Pakistan, and Afghanistan” by Ahmed Rashid (Viking/Penguin, 234 pages, $28.50)

American follies in Iraq and Afghanistan stretching over the past 13 years rivals a similar second-century Roman folly in Parthia, a folly during which Rome pursued elusive enemies in far-off lands with costly and uncertain goals in mind, supported by untrustworthy allies. Ahmen Rashid, a gallant Pakistani (any Pakistani who writes about his own country is gallant), has written a book about America and Pakistan, two countries linked by dissimilar illusions and burdened by similar disillusions.

In two previous books, “Taliban” and “Descent Into Chaos,” Rashid chronicled, respectively, the rise of the Taliban in Afghanistan and George W. Bush’s illegal and intemperate war in Iraq. Now, in “Pakistan on the Brink,” Rashid brings his considerable reportorial skills to bear on the curious relationship between America and Pakistan, with the focus on Pakistan’s furious dreamlike state of denial and its many-sided jihadist misdemeanors.

To sum it up, Pakistan sponsored the Taliban in Afghanistan originally as a Pashtun counterweight to India’s supposed military power on its eastern border. Run by the military, Pakistan is unstable and decaying financially, politically and ecologically. It has precious little fresh water, few natural resources, and is wildly overpopulated. Dozens of ethnic and sectarian groups cluster around an unbalasted central government run largely by the military for the military, a floundering midget sustained mainly by American largesse. And, of course, Pakistan has perhaps a hundred nuclear weapons.

America, for its part, has cast its lot with Pakistan’s military, hoping endlessly for support in its war with militant Islam. What country wouldn’t be disillusioned with an ally who allowed Osama Bin Laden to live freely within a few miles of a major military base?

The depth of this mutual disillusionment is the subject of Rashid’s book, which is written in a flat, dense naturalistic style that is unlikely to appeal to many reader’s deeper aesthetic feelings.

However, each chapter is a kind of history lesson well worth reading, especially among those inclined to wave the flag.